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[122.62.141.252]) by smtp.gmail.com with ESMTPSA id q16-20020a62ae10000000b00682b2fbd20fsm1933139pff.31.2023.08.18.13.44.50 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Aug 2023 13:44:55 -0700 (PDT) Subject: Re: [PATCH v2 2/3] ata: pata_falcon: add data_swab option to byte-swap disk data To: Finn Thain References: <20230818071405.28581-1-schmitzmic@gmail.com> <20230818071405.28581-3-schmitzmic@gmail.com> <16f01be8-de2e-4fb2-50c3-95f030e740ac@linux-m68k.org> Cc: dlemoal@kernel.org, linux-ide@vger.kernel.org, linux-m68k@vger.kernel.org, will@sowerbutts.com, rz@linux-m68k.org, geert@linux-m68k.org From: Michael Schmitz Message-ID: Date: Sat, 19 Aug 2023 08:44:47 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: <16f01be8-de2e-4fb2-50c3-95f030e740ac@linux-m68k.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Finn, Am 18.08.2023 um 19:43 schrieb Finn Thain: > > On Fri, 18 Aug 2023, Michael Schmitz wrote: > >> Some users of pata_falcon on Q40 have IDE disks in default >> IDE little endian byte order, whereas legacy disks use >> host-native big-endian byte order as on the Atari Falcon. >> >> Add module parameter 'data_swab' to allow connecting drives >> with non-native data byte order. Drives selected by the >> data_swap bit mask will have their user data byte-swapped to >> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap >> all user data on drive B, leaving data on drive A in native >> byte order. On Q40, drives on a second IDE interface may be >> added to the bit mask as bits 2 and 3. >> >> Default setting is no byte swapping, i.e. compatibility with >> the native Falcon or Q40 operating system disk format. >> >> Cc: William R Sowerbutts >> Cc: Finn Thain >> Cc: Geert Uytterhoeven >> Signed-off-by: Michael Schmitz >> >> --- >> >> Changes since v1: >> >> Damien Le Moal: >> - change patch title >> - drop swap_data flag >> >> Finn Thain: >> - drop allocation of ap->private struct, use field as bitmask >> >> Changes since RFC v4: >> >> Geert Uytterhoeven: >> - don't shift static module parameter for drive 3/4 bitmask >> - simplify bit mask calculation to always use pdev->id >> >> Finn Thain: >> - correct bit numbers for drive 3/4 >> >> Changes since RFC v3: >> >> - split off this byte swap handling into separate patch >> >> - add hint regarding third and fourth drive on Q40 >> >> Finn Thain: >> - rename module parameter to 'data_swab' to better reflect its use >> >> William Sowerbutts: >> - correct IDE drive number used in data swap conditional >> --- >> drivers/ata/pata_falcon.c | 10 +++++++++- >> 1 file changed, 9 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/ata/pata_falcon.c b/drivers/ata/pata_falcon.c >> index 346259e3bbc8..27443cb757de 100644 >> --- a/drivers/ata/pata_falcon.c >> +++ b/drivers/ata/pata_falcon.c >> @@ -33,6 +33,11 @@ >> #define DRV_NAME "pata_falcon" >> #define DRV_VERSION "0.1.0" >> >> +static int pata_falcon_swap_mask; >> + >> +module_param_named(data_swab, pata_falcon_swap_mask, int, 0444); >> +MODULE_PARM_DESC(data_swab, "Data byte swap enable/disable bitmap (0x1==drive1, 0x2==drive2, 0x4==drive3, 0x8==drive4, default==0)"); >> + >> static const struct scsi_host_template pata_falcon_sht = { >> ATA_PIO_SHT(DRV_NAME), >> }; >> @@ -46,11 +51,12 @@ static unsigned int pata_falcon_data_xfer(struct ata_queued_cmd *qc, >> void __iomem *data_addr = ap->ioaddr.data_addr; >> unsigned int words = buflen >> 1; >> struct scsi_cmnd *cmd = qc->scsicmd; >> + int dev_id = dev->devno; > > Is that variable really needed? Not really, no. > >> bool swap = 1; >> >> if (dev->class == ATA_DEV_ATA && cmd && >> !blk_rq_is_passthrough(scsi_cmd_to_rq(cmd))) >> - swap = 0; >> + swap = (uintptr_t)ap->private_data & BIT(dev_id); >> >> /* Transfer multiple of 2 bytes */ >> if (rw == READ) { >> @@ -199,6 +205,8 @@ static int __init pata_falcon_init_one(struct platform_device *pdev) >> ap->ioaddr.altstatus_addr = ctl_base + io_offset; >> ap->ioaddr.ctl_addr = ctl_base + io_offset; >> >> + ap->private_data = (void *)(uintptr_t)(pata_falcon_swap_mask >> (2 * pdev->id)); >> + > > My compiler doesn't need that extra type cast in there... Geert's suggestion for 64 bit safety... Cheers, Michael > >> irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0); >> if (irq_res && irq_res->start > 0) { >> irq = irq_res->start; >>